DIGESTION. 



65 



like the lid of a chest. Usually the epiglottis stands erect, 

 but the moment any food passes over the tongue, it is 

 instantly drawn down, and closes the opening into the wind- 

 pipe, so that the food is carried on to the gullet. If not 

 well closed, a little food or drink may " go the wrong way," 



Fro. 22. Section showing passages to the gullet and windpipe. 



and cause violent coughing and choking. Boisterous laughter 

 at table is sometimes suddenly and seriously checked in this 

 accidental way. 



The process of swallowing food is partially a voluntary and 

 partially an involuntary action of the muscles engaged. It is 

 by the individual's will that food or drink is carried into the 

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